The present invention relates to a speaker unit, in particular to a speaker unit which is thin in thickness and has an elliptical shape.
There has been known a thin type speaker unit which is for use in a television set and whose vibrating diaphragm is usually formed into an elliptical shape. On the other hand, it is usually required that a magnetic circuit of a speaker unit be formed in a manner such that it can provide a uniform magnetic flux to the surface of a cylindrical voice coil. Accordingly, it is often required that a top plate and a permanent magnet each having a circular doughnut shape be used so that the whole magnetic circuit has a cylindrical shape.
In fact, a thin type speaker unit usually has a magnetic circuit whose outer diameter is equal to or smaller than a width in a short axis direction of a frame structure which supports a vibrating diaphragm. In this way, a speaker unit as a whole may be made smaller, thus meeting with a requirement of making a compact speaker unit.
However, in a thin type speaker unit as above related, since a magnetic circuit has to be made small in size due to a restriction caused by a width in the short axis direction of a vibrating diaphragm, the magnetic flux to be applied to the surface of a voice coil will have a low density, resulting in a problem that the speaker unit has only a low sensitivity.